Recognized twice in recent years in Money Magazine's Top 100 Best Places to Live in the United States, the City of Longmont, Colorado is experiencing an increase in population. Known for outstanding Rocky Mountain views, open space and acres of parks, it's easy to see the appeal of the Longmont Life.
In keeping with their most recent wastewater treatment master plan that would allow the city to keep pace with an expanding population, initiatives were designated for the City's Public Works & Natural Resources Department. Included in these initiatives was a need to determine capacity requirements for their local wastewater treatment plant for estimated future build-out. Since that time, however, it was felt that the capacity requirements were somewhat overestimated and a flow-monitoring program was put in place to determine actual flow rates.
The City's wastewater collection system includes 326 miles of sanitary sewer lines and a wastewater treatment plant that has the capacity to treat 17 million gallons per day (MGD). Current average daily flow is 8.5 MGD. Planned future upgrades will bring the plant up to 21 MGD.
According to Chris Huffer, P.E., Civil Engineer, with the City of Longmont's Public Works & Natural Resources Department, "The city council adopted benchmarks and one of them was to monitor the depth and velocity of flow in our major trunk system in our interceptors."
Longmont had previously utilized open channel flow meters for portable flow monitoring applications. In 2002 when flow meters for permanent AC powered sites were required, a request for quote was developed and subsequently awarded to Hach Company for their Sigma Model 950 Flow Meters. Huffer adds, "The Sigma Model 950 flow meter came to the top of the list! We like the accessible keypad and the larger screen really makes it easy to use the internal electronics."
Longmont currently owns (9) Sigma Model 950 flow meters that are connected to their SCADA system. The meters are collecting data in their trunk system in sewer line sizes from 27" to 42". For the city's monitoring program, the meters are installed in March and removed in the October to November timeframe. Hach's InSight Software is utilized in addition to the data being collected by the SCADA System. Huffer adds, "We use InSight to do downloads on a bi-monthly basis just to check the data that is in the collector with what we've been collecting with our SCADA. InSight works great for us! The reporting capabilities break it down by week or day, or whatever we want." Final flow data from the meters is funneled through the City's engineering group for final report preparation prior to being provided to the City Council.
In 2005, the City again had a requirement for a portable flow meter that would be moved from site-to-site to assist personnel in their Inflow & Infiltration (I&I) monitoring locations. Additionally, there was a monitoring location within the collection system that had proven difficult to measure with submerged sensors due to sediment build-up in the 27" line.
Personnel were introduced to Hach's Marsh-McBirney Flo-Dar Flow Meter. The award-winning Flo-Dar flow meter provides a revolutionary approach to open channel and sewer flow monitoring by utilizing a non-contact radar velocity/area sensor. Flo-Dar's unique non-contact measuring technology means trouble-free sewer flow monitoring. The sensor utilizes digital doppler radar velocity sensing technology with ultrasonic pulse echo level sensing. Independent testing performed by Alden Laboratory confirms Flo-Dar's accuracy, as does the satisfaction of thousands of users worldwide.
Huffer comments, "The Flo-Dar has been great. We've had no issues, it's very low maintenance and the data is very accurate. It's actually worked out very well in our trunk system and it's been our best installation."
Click here to take a virtual tour of the City of Longmont's Wastewater Treatment Plant.